With finer semiconductor integrated circuits (IC), there have been demanded lower IC voltages and I/O signal voltages. Meanwhile, in situations in which host apparatuses and extension devices compatible with high power-supply voltages are distributed, host apparatuses and extension devices compatible with high power-supply voltage interfaces and low power-supply voltage interfaces may be used in mixture.
When the input of an input buffer is in a floating state or a middle voltage is input into the input buffer, a flow-through current may flow into the input buffer. In particular, the high level of a low voltage signaling may be a middle voltage of a high voltage signaling. Accordingly, when host apparatuses and extension devices operating under different signal voltages are connected, a flow-through current may flow into the input buffer. Hereinafter, the high voltage signaling will be expressed as HVS and the low voltage signaling will be expressed as LVS.